Think US Clean Air Regulations Don't Work? Check Out Which Cities in the World Are Dirtiest

Cities in Iran were the first and third worst-polluted in this analysis. Photo: Hamid Najafi/CC BY ND

Most TreeHugger readers probably don't need convincing that strong regulations on air pollution are a good thing for personal and environmental health. If you need a graphic example though, check out what cities in the world have the worst air pollution and which have the least, according to the World Health Organization.

Map of worldwide air pollution: NASA. Note, these colors are based on a smaller size of air pollution particle than talked about here by the WHO, so it's not directly representative. Rather, take it as an overview of worldwide air pollution.

As The Guardian reports, WHO stats show that Ahvaz, Iran has the highest measured level of particulate air pollution smaller than 10 micrometers (PM10s)--372 micrograms per cubic meter. The WHO recommended upper limit is just 20 micrograms per cubic meter.

The second worst city was Ulan Bator, Mongolia (279 micrograms per cubic meter); the third was Sanandaj, Iran (254).

The WHO stats show that cities in Pakistan and India (Quetta in Pakistan and Kanpur in India were specifically cited), as well as Botswana's capital, as being highly polluted.

On the other end of the scale: Whitehorse, Canada had just 3 micrograms per cubic meter of PM10s; Santa Fe, New Mexico had 6; Washington DC had 18.

The source of this air pollution: Sulphur dioxide and nitrogen dioxide from power generation, motor vehicle exhaust, industry.